Quase tudo em /usr
pertence a root:root
Eu corro find /usr -not -gid 0 -printf "%M\t%u\t%g\t%p\n"
usando 15.04 e a saída é
-r-xr-sr-x root postdrop /usr/sbin/postqueue
-rwsr-xr-- root dip /usr/sbin/pppd
-r-xr-sr-x root postdrop /usr/sbin/postdrop
drwxrwsr-t root lpadmin /usr/share/ppd/custom
drwxrwsr-x root staff /usr/local/share/xml
drwxrwsr-x root staff /usr/local/share/xml/declaration
drwxrwsr-x root staff /usr/local/share/xml/entities
drwxrwsr-x root staff /usr/local/share/xml/schema
drwxrwsr-x root staff /usr/local/share/xml/misc
drwxrwsr-x root staff /usr/local/share/emacs
drwxrwsr-x root staff /usr/local/share/emacs/site-lisp
drwxrwsr-x root staff /usr/local/share/sgml
drwxrwsr-x root staff /usr/local/share/sgml/declaration
drwxrwsr-x root staff /usr/local/share/sgml/entities
drwxrwsr-x root staff /usr/local/share/sgml/dtd
drwxrwsr-x root staff /usr/local/share/sgml/stylesheet
drwxrwsr-x root staff /usr/local/share/sgml/misc
drwxrwsr-x root staff /usr/local/share/ca-certificates
drwxrwsr-x root staff /usr/local/share/fonts
drwxrwsr-x root staff /usr/local/lib/python3.4
drwxrwsr-x root staff /usr/local/lib/python3.4/dist-packages
drwxrwsr-x root staff /usr/local/lib/python2.7
drwxrwsr-x root staff /usr/local/lib/python2.7/dist-packages
drwxrwsr-x root staff /usr/local/lib/python2.7/site-packages
drwxr-xr-x root utempter /usr/lib/utempter
-rwxr-sr-x root utmp /usr/lib/utempter/utempter
-rwxr-sr-x root mail /usr/lib/evolution/camel-lock-helper-1.2
-rwsr-xr-- root messagebus /usr/lib/dbus-1.0/dbus-daemon-launch-helper
-rwxr-sr-x root utmp /usr/lib/libvte-2.91-0/gnome-pty-helper
-rwxr-sr-x root crontab /usr/bin/crontab
-rwxr-sr-x root tty /usr/bin/wall
-rwxr-sr-x root tty /usr/bin/bsd-write
-rwxr-sr-x root shadow /usr/bin/chage
-rwxr-sr-x root shadow /usr/bin/expiry
-rwxr-sr-x root mail /usr/bin/mail-unlock
-rwxr-sr-x root mlocate /usr/bin/mlocate
-rwxr-sr-x root mail /usr/bin/dotlockfile
-rwxr-sr-x root mail /usr/bin/mail-touchlock
-rwxr-sr-x root mail /usr/bin/mail-lock
-rwxr-sr-x root ssh /usr/bin/ssh-agent
-rwsr-sr-x daemon daemon /usr/bin/at
e, dada a saída, não vejo o que você pode ter errado para conseguir o que descreve. Pode ser o material do dbus ...
Mas você pode, no entanto, manualmente chown o arquivo acima para tentar recuperar o seu Ubuntu.
você pode não ter os mesmos arquivos ou eu posso perder alguns de seus arquivos, então mesmo que você manualmente mostre os arquivos acima, você não está totalmente pronto para isso.